This invention relates to packaging materials having oxygen barrier quality.
Packaging materials in current use are mostly made of polymers that can be easily processed into various shapes such as films, sheets, bottles and vessels and which are also lightweight to permit transportation at low cost.
When the materials to be packed are food and other substances that are prone to deteriorate by oxidation, packaging materials are required to have particularly high oxygen barrier quality. To meet this need, polymers of high oxygen barrier quality such as the saponification product of an ethylene-vinyl acetate copolymer (EVOH) and polyvinylidene chloride, as well as films with evaporated coatings of aluminum or silicon oxides have been used. However, the polymers having high oxygen barrier quality have been too expensive to be commercialized. In addition, EVOH has the problem that its oxygen barrier quality decreases upon moisture absorption. The films with evaporated coats suffer the disadvantage that pinholes or cracks will prevent them from exhibiting the intended oxygen barrier quality in a consistent manner.
The present inventors previously filed a Japanese patent application (now published as Unexamined Published Japanese Patent Application Hei 4-213346) and proposed a polyolefinic resin composition that dispensed with costly resins having oxygen barrier quality by using a polyolefin and an oxidation catalyst and which yet would exhibit satisfactory oxygen barrier quality over time. However, this polyolefinic resin composition which is intended to exhibit oxygen barrier quality over time has had the problem that if it is rendered as a film with a thickness of 100 .mu.m and less, the intended oxygen barrier quality is not fully exhibited right after processing into the film.